A slalom boot should transfer the movements of the foot precisely as a force directed at the ski. On the other hand, a slalom boot should fit the individual foot of the user without any feeling of cramping. In accordance with the known technique it is as such possible to shape a boot entirely in accordance with the user's foot by first choosing a large outer shell and by fitting the inner boot to the shape of the user's foot with the aid of urethane foam. Operationally a boot of this kind is not, however, optimal, because the excessive flexibility of the inner boot reduces the technical operation of the boot.
In certain slalom boot models there are adjustments to alter the height of the arch of the foot and to tilt the ankle to a limited amount to a desired angle. In any event the boot is not a perfect fit for most users and it is generally believed that a slight cramping by the boot is normal.
Because the costs of the forms used in the manufacture of the outer shell are high, it is not possible to manufacture even different shapes in the same model and size. On the other hand even this would not be sufficient, because there is such an immense number of combinations of different anatomical properties that a solution of this kind is not possible.
A slalom boots and implements to shape it locally in accordance with the user's foot are shown in patent publication U.S. Pat. No. 3,419,974. According to this a piece to be heated is pressed outwards from inside the shell of the boot. In practice shaping of a boot with an implement of this kind is rather limited unless high temperatures are used in heating it, which may then damage the plastic material of the boot. The grades of plastic used at present in boots stick easily to a heating head. On the other hand the publication gives no hint as to how the anatomical form of the foot is transferred to the inside of the boot in the form of directions for shaping.